Judgments about the validity of at least some elementary inferential patterns(say modus ponens) are a priori if anything is. Yet a number of empirical conditions mustin each case be satisfied in order for a particular inference to instantiate this or that inferentialpattern. We may on occasion be entitled to presuppose that such conditions aresatisfied (and the entitlement may even be a priori), yet only experience could tell us thatsuch was indeed the case. Current discussion about a perceived incompatibility betweencontent externalism (...) and first-person authority exemplifies how damaging the neglect ofsuch empirical presuppositions of correct reasoning can be. An externalistic view of mentalcontent is ostensibly incompatible with the assumption that a rational subject should beable to avoid inconsistency no matter what the state of her empirical knowledge may be.That fact, however, needs not be taken (as it often is) as a reductio of externalism: alternatively,we may reject that assumption, adding to the agenda of a philosophical investigationof rationality an examination of the vicissitudes of logical luck. I offer an illustrationand defense of that alternative. (shrink)